Indicating instrument for vehicle

ABSTRACT

A straight cold cathode fluorescent lamp is detachably held at the back of a dial plate by a plurality of fork-shaped holders to illuminate a plurality of scales formed on the front surface of the dial plate and accommodated in the reflector which is also detachably fixed to a casing of the indicator instrument. A circuit board is also detachably fixed to the reflector.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an indicating instrument for varioususes and, particularly, a vehicular indicating instrument having a lightsource such as a cold cathode fluorescent lamp driven by high voltagepower.

2. Description of the Related Art

JPB2-7-107490 disclose s an indicating instrument which has a circularcold cathode fluorescent lamp for illuminating a dial plate andindicators. Because the cold cathode fluorescent lamp is circular, it isnecessary to provide various types and sizes of cathode fluorescentlamps for a plurality of types of indicating instruments.

SUMMARY OF THE INVENTION

The present invention has an object of providing an improved indicatinginstrument which has a simple structure and can be used for varioustypes of vehicles.

For this object, an indicating instrument for a vehicle has a generallystraight lamp extending in the longitudinal direction of the dial plate,a light conducting plate disposed on the back surface of the dial plate,and a reflector for accommodating the light source and reflecting lightof the light source to the light conducting plate.

Another object of the present invention is to provide an indicatinginstrument having a lamp which is easily replaced.

For this object, an indicating instrument has, in addition to the abovestructure, means detachably fixed to the casing of the indicatorinstrument to combine the light source and the reflector. Preferably, acircuit board is detachably fixed to the reflector.

In addition to the above feature, an indicating instrument preferablyhas a detachable connector, which has a terminal plate connecting thelight source to a high-voltage source and other terminal plates, and theterminal plate is disposed at a distance large enough to insulate itfrom other terminals.

Another object of the present invention is to provide an indicatinginstrument wherein the light source can be removed by an action in thelongitudinal direction of the casing.

For this object, a fixing member is fixed to the casing for detachablyholding the reflector in the longitudinal direction and an opening isformed in the casing so that the reflector and light source can passthrough the opening when they are removed from the casing in thelongitudinal direction.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and characteristics of the present invention aswell as the functions of related parts of the present invention willbecome clear from a study of the following detailed description, theappended claims and the drawings. In the drawings:

FIG. 1 is a front view of an indicating instrument according to a firstembodiment of the present invention;

FIG. 2 is a cross-sectional view taken along a line II--II of FIG. 1;

FIG. 3 is a front view illustrating a main portion of a connector of anindicating instrument according to the first embodiment viewed from adirection indicated by an arrow A of FIG. 2;

FIG. 4 is a cross-sectional view illustrating the connector taken alonga line IV--IV of FIG. 3;

FIG. 5 is an exploded view of a lamp unit shown in FIG. 1;

FIG. 6 is a circuit diagram of the indicating instrument according toembodiments of the present invention;

FIG. 7 is a main part of a variation of the lamp unit shown in FIG. 5;

FIG. 8 is a front view illustrating an indicating instrument accordingto a second embodiment of the present invention;

FIG. 9 is a cross-sectional view of a main portion of the indicatinginstrument taken along a line IX--IX of FIG. 8;

FIG. 10 is an exploded view of a lamp unit of the indicating instrumentaccording to the second embodiment;

FIG. 11 is a front view illustrating a main portion of a variation ofthe connector of an indicating instrument according to the embodimentsof the present invention;

FIG. 12 is a front view of the connector shown in FIG. 11 in thedisconnected state;

FIG. 13 is a cross-sectional view illustrating the connector taken alonga line XIII--XIII of FIG. 11;

FIG. 14 is a cross-sectional view illustrating a main portion of anindicating instrument according to a third embodiment of the presentinvention;

FIGS. 15A and 15B are cross-sectional views illustrating a lamp unitincluding a lamp, a reflector and a circuit board;

FIG. 16 is a cross-sectional view illustrating a main portion of anindicating instrument according to a fourth embodiment of the presentinvention;

FIG. 17 is a front view of the main portion illustrated in FIG. 16viewed from a portion indicated by an arrow B in FIG. 16;

FIG. 18 is a side view illustrating a variation of a hold member;

FIGS. 19A and 19B are a side view and a front view illustrating anothervariation of the hold member;

FIGS. 20A and 20B are cross-sectional views illustrating a lamp unitincluding a lamp and a reflector according to a fifth embodiment of thepresent invention;

FIG. 21 is a variation of a casing of the indicating instrumentaccording to the embodiments of the present invention;

FIG. 22 is a perspective view illustrating another variation of thecasing; and

FIGS. 23A, 23B and 23C are perspective and cross-sectional viewsillustrating other variations of the casing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

An indicating instrument 10 according to a first embodiment is describedwith reference to FIGS. 1-6.

As shown in FIGS. 1 and 2, the indicating instrument 10 is composed of adial plate 10a, a straight cold cathode fluorescent lamp 10b, a lightconducting plate 10c, a light reflector 10d which has an L-shapedcross-section, a circuit board 70, a connector 80 and a circuit board90.

The dial plate 10a has a black surface on which scales 11, 12, 13 and 14of engine rotational speed (r.p.m.), vehicle speed (km/h), enginecoolant temperature (H, C) and fuel amount (F,E) in the fuel tank arerespectively formed in a well-known manner. The black surface issurrounded by an annular wall member 20 and covered by a transparentfront panel 30.

The lamp 10b is disposed behind the dial plate 10a in the longitudinaldirection of the dial plate 10a at an upper portion (left in FIG. 2)thereof and detachably fixed to a wall 17 of the reflector 10d by a pairof cylindrical holders 16 and a pair of forked clamps 17a as shown inFIGS. 1 and 5. The lamp 10b is long enough to illuminate all the scales11-14 and lamp 10b is provided with a heat wire H wound on the surfacethereof over the full length of the lamp 10b as shown in FIG. 5 andelectrically connected as shown in FIG. 6.

The light conducting plate 10c is made of an acrylic resin and fixed tothe back of the dial plate 10a under the lamp 10b so that the lightincidence portion 15 thereof faces the lamp 10b. The back of the lightconducting plate 10c is frosted to diffuse light so that light cominginto the conducting plate 10b from the light incidence portion 15 can bediffused by the back of the light conducting plate 10c and conducted tothe scales 11, 12, 13 and 14 effectively.

The reflector 10d is detachably fixed to the dial plate 10a and a casing60 to cover the lamp 10b. As shown in FIG. 5, the reflector 10d has aplurality of claw members 17b extending toward the circuit board 70, aplurality of claw members 17c extending in the direction opposite to thecircuit board 70 (toward the casing 60) and a side wall 18.

The scales 11, 12, 13 and 14 are equipped with indicators respectively,which are driven by driving units. An indicator 40 and a driving unit 50for the engine r.p.m. scale 11 are shown in FIG. 2.

The driving unit 50 is housed in the casing 60 and has a rotary shaft 51extending through a hole of the dial plate 10a to the front thereof tosupport the indicator 40.

The casing 60 has a flange 61, which has a plurality of slits into whichthe claw members 17c of the reflector 10d are fitted as shown in FIG. 2.At the same time, the side wall 18 of the reflector 10d abuts againstthe back of the dial plate 10a.

As shown in FIG. 5, the circuit board 70 has a plurality of openings 71receiving the claw members 17b of the reflector 10d so that the circuitboard 70 can be detachably fixed to the back of the reflector 10d. Thecircuit board 70 has a pair of terminals T1 and T2 connected to the lamp10b, a pair of forked terminals 72 which hold the terminals H1 and H2 inthe arms thereof at the opposite ends of the circuit board 70 to make aelectrical connection and a connector portion 74 into which a connector80 (see FIG. 4) is inserted, as shown in FIG. 5. Thus, the lamp 10b,reflector 10d and circuit board 70 compose a lamp unit U.

When the lamp 10b is going to be replaced due to a breakdown thereof,the lamp unit U is detached from the casing 60. Therefore, thereplacement of the lamp 10b can be carried out very easily.

As shown in FIGS. 3 and 4, the connector 80 is composed of a case 81made of an insulating material and a terminal unit 82 inserted in thecase 81 and is disposed between both circuit boards 70 and 90.

As shown in FIGS. 3 and 6, the terminal unit 82 has a terminal plate 82aconnected between the terminal 101 of the high-voltage-power generator100 and the terminal T1 of a circuit board 70 connected to the lamp 10b,and another terminal plate 82b connected between the terminal 102 of thehigh-voltage-power generator 100 and the terminal T2 of the circuitboard 70 connected to the lamp 10b.

As shown in FIGS. 3 and 4, the terminal unit is composed of a pluralityof terminal plates 82a, 82b, 82c, 82d and 82e which are disposedrespectively in grooves 81a, 81d, 81g, 81h and 81i formed in the case 81and soldered to respective terminals of the circuit board 70 and 90. Aninterval of the terminal plates 82a, 82b and 82c between each other isthree times as long as an interval of the terminal plates 82c, 82d and82e between each other, because the terminal plates 81a and 82b areconnected to the terminals 101 and 102 of the high-voltage-powergenerator 100 to supply the high-voltage power to the lamp 10a as shownin FIG. 6. The other terminal plates 82c, 82d and 82e are connected tothe ignition switch IG and the driving unit 50 respectively through thecircuit boards 70 and 90.

The circuit board 90 is fixed to the back of the casing 60 in parallelwith the circuit board 70 by a plurality of bolts and has thehigh-voltage-power generator 100 thereon, which has the terminals 101and 102.

The high-voltage-power generator 100 is powered by a battery Ba throughan ignition switch IG and generates, across the terminals 101 and 102,electric power of a voltage between hundreds of volts and tens ofthousand volts at a frequency of tens of kilohertz.

A heater circuit 110 supplies the heater H with electric power accordingto a signal of temperature of the lamp 10b sent from a thermistor 111when a normally-closed switch 120 made of a thermosensitive material isclosed, and the cold cathode fluorescent lamp 10b illuminates the dialplate 10b through the light conducting plate 10c. The thermistor 111 hasa pair of lead terminals, which are soldered to the circuit board 70.The terminals T1 and T2 of the lamp 10b are also soldered to the circuitboard 70 at opposite sides thereof. As the heater H heats the lamp 10band temperature of the surface of the lamp 10b exceeds a certain valuewhich indicates a normal temperature condition, the switch 120 is turnedoff.

The switch 120 is disposed in a space sealed by the dial plate 10a,reflector 10d, light conducting plate 10c and the flange 61 of thecasing 60 in order to keep accurate switching performance.

A variation of the indicating instrument according to the firstembodiment is shown in FIG. 7. The circuit board 70 is omitted, and thecold cathode fluorescent lamp 10b, the heater H and the thermistor 111are respectively connected to the terminal plates 82 of the connector 80by a plurality of lead wires L. The thermistor 111 is held by a holder16a which is mounted on the middle of the lamp 10b. Other portions arethe same in structure as the indicating instrument according to thefirst embodiment.

Second Embodiment

An indicating instrument according to a second embodiment is describedwith reference to FIGS. 8-10. The light conducting plate 10c, reflector10d, casing 60 and circuit board 70 in the first embodiment are replacedwith a light conducting plate 10e, a casing 10f, a reflector 130 and acircuit board 140 respectively. Other portions having the same referencenumeral as the first embodiment are substantially the same in structureand function, and therefore description is omitted.

The casing 10f has a longitudinal conduit 19 for accommodating the lamp10b, which faces the light conducting plate 10e through an opening 19awhich opens to the light incidence portion of the light conducting plate10e. The light incidence portion has a reflecting surface 19b facing thelamp 10b on the back thereof. The lamp 10b is secured by the reflector130; the circuit board 140 is detachably fixed to the back of thereflector 130; and the circuit board 90 is fastened to the casing 10f byscrew bolts.

As shown in FIG. 10, the reflector 130 has a base plate 131, both a pairof forked members 132 and a plurality of claw members 135 disposed on asurface of the base plate 131 and a plurality of claw members 133 on theopposite surface. The forked member 132 holds the lamp 10b by its ownresiliency at opposite ends thereof. The circuit board 140 has aplurality of openings 141 which receive the claw members 133 detachablyand a connector portion 142 disposed at a portion adjacent to thereflector 130. The terminals T1, T2 of the lamp 10b, terminals H1, H2 ofthe heater H and leads of both the thermistor 111 and the switch 120pass through the base plate 131 of the reflector 130 and are inserted inholes of solder lands and soldered thereto respectively.

The thermistor 111 is held in a groove of a holder 16b separate from agroove holding the lamp 10b. The thermistor 111 and switch 120 arehoused in compartments 134a and 134b of the reflector 130 respectively.Thus, the lamp 10b, reflector 130 and circuit board 140 compose adetachable lamp unit Ub.

The connector 80 is connected to the connector portion 142 afterassembling of the lamp unit Ub. The reflector 130 is, thereafter, fixedto the casing 10f by the claw members 135 fitted in slits of the casing(not shown) as described before.

If the lamp has to be replaced with a new one, the unit Ub is detachedfrom the casing 10f. It is not necessary that the lamp 10b is strictlystraight. The lamp 10b can be a generally straight lamp of some othertype such as a xenon lamp. The reflector can be detachably fixed to thelight conducting plate or the dial plate also.

The heater H can control the brightness of the lamp by changing wirecolor or number of turns of the wire in places.

A variation of the connector 80 is described with reference to FIGS.11-13.

The connector 80 in the first embodiment is replaced with first andsecond connectors 180 and 190 in the third embodiment.

As shown in FIGS. 11 and 12, the first connector 180 is composed of apair of connector cases 181a and 181b made of insulating material and aplurality of terminal plates 182a-182e made of conducting material.

The connector case 181a has a pair of fixing pins 181c fitted intothrough holes 71 formed in the circuit board 70, and the connector case181b is fixed to the circuit board 90 by a pin 92 or the like.

As shown in FIG. 13, each of the terminal plates 182a-182e ispress-fitted into one of holes 183a and 183b of the connector cases 181aand 181b, and each of the lower ends of the terminal plates 182a-182e isinserted into one of through holes 91 formed in the circuit board 90 andsoldered thereto.

As shown in FIG. 13, the second connector 190 is fixed to the uppersurface of the circuit board 70 and is composed of a case 191, upperportions of the terminal plates 182a-182e inserted in holes 191a formedin the case 191 and a plurality of S-shaped spring terminals 192a-192e(only 192c is illustrated in FIG. 13) disposed in the case 191 to biasagainst the terminal plates 182a-182e (the spring terminal 192c biasesthe terminal plate 182c in FIG. 13) respectively.

The interval between adjacent ones of the terminal plates 182a-182c isthe same as the interval between adjacent ones of the terminal plates82a-82c of the connector 80 of the first embodiment, and the intervalbetween adjacent ones of the terminal plates 182c-182e is the same asthe interval between adjacent ones of the terminal plates 82c-82e of thefirst embodiment. The terminal plates 182a and 182b are connectedbetween the high-voltage power source 100 and the cold cathodefluorescent lamp 10b as in the same manner shown in FIG. 6.

The interval of terminal plates 82a-82e and 182a-182e can be held by anadhesive tape instead of the connector cases 81, 181a, 181b and 191.

Third Embodiment

An indicating instrument according to a third embodiment is describedwith reference to FIGS. 14, 15A and 15B. The circuit board 70 abuts thebottom surface of wing members 17u and 17v which are formed on theopposite sides of the wall 17 of the reflector 10d to face the lamp 10bvia the wall 17. The circuit board is fixed to the bottom surface of thelight conducting plate 10c by a plurality of screw bolts 70b (FIG. 14shows only one screw bolt) via sleeves 70a.

As shown in FIG. 15A, connectors 171 and 172 are fixed to the uppersurface of the circuit board 70 respectively by the left side of thewing members 17u and 17v.

The connector 171 is composed of a connector body 171a and an L-shapedconnector terminal 171b. The connector body 171a is fixed to the uppersurface of the circuit board 70 and has an open space 171d. The L-shapedconnector terminal 171b passes through the circuit board 70 and extendsin the open space 171d in parallel with the circuit board 70. Theconnector pin 171c is disposed to align with the connector terminal 171band passes through the side wing 17u so that the connector pin 171c canhold the connector terminal 171b detachably. The terminal T2 of the lamp10b is connected to the connector pin 171c through the wall of thereflector 17.

As shown in FIG. 15A, the open space 171d of the connector body 17a isdetachably fitted to a projecting portion 17w of the wing member 17u.

On the other hand, the connector 172 is composed of a connector body172a and an L-shaped connector terminal 172b. The connector body 172a isfixed to the upper surface of the circuit board 70 and has an open space172d. The L-shaped connector terminal 172b passes through the circuitboard 70 and extends in the open space 172d of the connector body 172ain parallel with the circuit board 70. The connector pin 172c isdisposed to align with the connector terminal 172b and passes throughthe side wing 17v so that the connector pin 172c can hold the connectorterminal 172b detachably. The terminal T1 of the lamp 10b is connectedto the connector pin 172c through the bottom wall 17 of the reflector10d. The open space 172d is detachably fitted to a projecting portion17x of the wing member 17v.

The circuit board 70 has an engagement hole 73 near the right surface ofthe wing member 17u as shown in FIG. 15B so that a hook 119d of anL-shaped arm 119c, which extends from a hold portion 119 of thereflector 10d, engages the engagement hole 73. The hold portion 119 hastwo grip ends 119a and 119b extending toward an opening 61a which isformed in the right wall of the casing 60. The two grip ends 119a and119b bend inward to swing the arm 119c outward when they are compressedby two fingers.

The opening 61a has a size large enough to allow human fingers to passtherethrough.

One end of the connector 80 is connected to the connector terminals 171band 172b of the connectors 171 and 172 through the circuit board 70, andthe other end of the connector 80 is connected to the circuit board 90.The remaining structure is almost the same as the first embodiment.

When the lamp 10b is to be removed, insert fingers into the opening 61aof the casing 60 and compress the grip ends 119a and 119b so that thehook 119d of the L-shaped arm can disengage from the engagement hole 73as shown in FIG. 15B. Then, pass the hold portion 119 through theopening 61a and pull the grip ends 119a and 119b together with the lamp10b and the reflector 10d toward the outside of the opening 61a. As aresult, the connector pins 171c and 172c and the projecting portions 17wand 17x are subsequently disengaged from the connector terminals 171band 172b and the open spaces 171d and 172d respectively, and finally thelamp 10b and the reflector 10d can be pulled out of the casing 60.

Fourth Embodiment

A fourth embodiment is described with reference to FIGS. 16 and 17.

A reflector 10d is similar to that of the first embodiment, and a holdmember 200 is adopted in this embodiment.

As shown in FIG. 17, the hold member 200 is detachably fixed to theright side of the light conducting plate 10c to hold the reflector 10d.The hold member 200 is composed of a plate member 201 made of an elasticresin and a leaf spring 202. The plate member 201 has two pressor plates201a extending over opposite surfaces of the light conducting plate 10cto hold the light conducting plate 10c at the both sides thereof (onlyone pressor plate 201a is shown in FIG. 17). A grip portion 201b isformed at an upper portion of the hold member 200.

The leaf spring 202 has a convex surface facing the reflector 10d sothat the hold member 200 pushes the reflector 10d toward the left inFIG. 17 elastically against a left side wall of the circuit board 70,thereby holding the reflector 10d. Other portions are substantially thesame as those of the third embodiment.

When the lamp 10b is to be removed from the casing 60 through theopening 61a, insert fingers into the casing 60 through the opening 61a,hold the grip portion 201b by fingers to disengage the hold member 200from the light conducting plate 10c, pull the reflector 10d togetherwith the circuit board 70 and the lamp 10b through the opening 61a outof the casing 10.

A variation of the hold member 200 is shown in FIG. 18. The leaf spring202 is replaced with a rubber member 204.

Another variation of the hold member 200 is shown in FIGS. 19A and 19B.

This hold member 200, is composed of a leaf spring 211 and a screw bolt212. A lower end of the leaf spring 211 is rotatably fixed to a sideportion of the light conducting plate 10c by the screw bolt 212 tonormally press an end of the reflector 10d as shown in FIG. 19A. Whenthe lamp 10b and the reflector 10d are to be removed, the leaf spring isturned as shown in FIG. 19B.

Fifth Embodiment

A fifth embodiment of the present invention is described with referenceto FIGS. 20A and 20B. The reflector 10d of the fourth embodiment isreplaced with a reflector 10f in this embodiment.

The reflector 10f has a U-shaped cross section and is fixed to thecircuit board 70 as shown in FIG. 20B. The reflector 10f has a pair ofconnector terminals 219e which extend inside the reflector 10f todetachably connect the terminal T1 of the lamp and the terminal H1 ofthe heater respectively. A connector 220 has a cylindrical connectorbody 221 and a pair of latches 222 having hooks 222a and extendinglongitudinally from the connector body 221. A pair of connectorterminals 223 extend in the connector body 221 from the bottom wallthereof.

When the connector body 221 is moved to the left side of the reflector10f as shown in FIG. 20A, the latches 222 are inserted into engagementholes 219f. At the same time a pair of connector terminals 223 aredetachably connected to the terminal T2 of the lamp 10b and the terminalH2 of the heater H. In this embodiment, the connection strength of theconnector terminal 223 is set to be stronger than the connectionstrength of the connector terminals 219e. The connector terminals 223are connected to the circuit board 70 by a connector 224 as shown inFIG. 20B.

Other portions are substantially the same as those of the fourthembodiment.

When the lamp 10b and the reflector 10f are to be removed, press bothlatches by fingers to disengage the hooks from the engagement holes 219fand pull the connector body 221 out of the casing 60 through the opening61a. The terminals T1 and H1 are removed from the connector terminals219e first.

After removing the connector 224 from the circuit board 70, the lamp 10band the connector 220 are pulled out of the casing 60 through theopening 61a, and the connector terminals 223 are removed from theterminals T2 and H2.

A variation of the above embodiment is shown in FIG. 21. A cover member60a having a knob 62 is formed on the casing 60 to cover the opening61a.

Another variation of the fifth embodiment is shown in FIG. 22. A filtermember 60b is detachably disposed in a groove formed along the innerperiphery of the opening 61a.

Other variations are shown in FIGS. 23A, 23B and 23C.

The opening 61a of this embodiment is covered by an integrated covermember 60c which is generally surrounded by V-shaped grooved portions 63as shown in FIG. 23A or grooved portions 65 as shown in FIG. 23B, whichis a cross-sectional view cut along a line indicated by arrows 23B inFIG. 23A. The integrated cover member 60c can be formed by cutting thecasing 60 except for connecting portions 66 as shown in FIG. 23C. Thecover member 60c shown in FIGS. 23A, 23B and 23C has a handle 64 so thatthe cover member 60c can be torn off along the grooved portions 63 or 65or at the connecting portions 66 by pulling the handle 64.

The covers and filter member described above are not only effective toprevent foreign particles from entering the interior of the case 60 butalso add a fine appearance of the case.

In the foregoing description of the present invention, the invention hasbeen disclosed with reference to specific embodiments thereof. It will,however, be evident that various modifications and changes may be madeto the specific embodiments of the present invention without departingfrom the broader spirit and scope of the invention as set forth in theappended claims. Accordingly, the description of the present inventionin this document is to be regarded in an illustrative, rather thanrestrictive, sense.

What is claimed is:
 1. An indicating instrument for a vehicle, saidinstrument comprising:a casing; a longitudinally extending dial platefixed in place relative to said casing, said dial plate having aplurality of indicating gauges disposed on a front surface thereof; alight source disposed to extend in the longitudinal direction of saiddial plate; a light conducting plate disposed on the back surface ofsaid dial plate, said light conducting plate having a light incidencesurface facing said light source; and a reflector, for reflecting lightof said light source to said light incidence surface of said lightconducting plate, detachably fixed to said casing.
 2. An indicatinginstrument as claimed in claim 1, wherein said first member comprises apair of forked clamps.
 3. An indicating instrument as claimed in claim 1further comprising a circuit board detachably fixed to said reflector.4. An indicating instrument as claimed in claim 1, wherein said casinghas a slit, andsaid second member comprises a claw member in engagementwith said slit of said casing.
 5. An indicating instrument as claimed inclaim 4, whereinsaid casing has a longitudinal conduit, and saidreflector is disposed in said conduit.
 6. An indicating instrument asclaimed in claim 1, whereinsaid light source comprises a tubular lamp, aheater disposed on said lamp, a thermosensitive element disposed nearsaid heater and a switch connected to said heater, and a temperature ofsaid heater is controlled by said switch.
 7. An indicating instrument asclaimed in claim 6, whereinsaid switch is fixed to said reflector.
 8. Anindicating instrument as claimed in claim 6, whereinpower supplied tosaid heater is cut by said switch when said thermosensitive elementdetects that said temperature of said heater is in a normal condition.9. An indicating instrument as claimed in claim 1 further comprising:ahigh-voltage-power source and a connector, wherein said connector has aterminal plate connecting said light source to said high-voltage sourceand other terminal plates, and said terminal plate connecting said lightsource to said high-voltage-power source is disposed at a distance largeenough to insulate said terminal plate connecting said light source tosaid high-voltage-power source from other terminal plates.
 10. Anindicating instrument as claimed in claim 9, wherein:said connectorcomprises an insulating member having a plurality of grooves, one ofwhich is disposed at an interval large enough to insulate a terminalplate from other terminal plates, and said terminal plate connectingsaid light source to said high-voltage power source is disposed in saidone of said plurality of grooves.
 11. An indicating instrument for avehicle, said instrument comprising:a casing; a longitudinally extendingdial plate fixed in place relative to said casing, said dial platehaving a plurality of indicating gauges disposed on a front surfacethereof; a light source disposed to extend in the longitudinal directionof said dial plate; and a reflector, disposed in said casing, foraccommodating said light source and reflecting light of said lightsource to said dial plate; wherein said casing comprises a first memberfor detachably fixing said reflector to be removed in the longitudinaldirection of said dial plate, and said casing has an opening forallowing said reflector and said light source to pass therethrough whenthey are removed from said case in the longitudinal direction of saiddial plate.
 12. An indicating instrument as claimed in claim 11 furthercomprising a longitudinally extending circuit board detachably fixed tosaid reflector and connected to said lamp so that said reflector, lightsource and circuit board can pass through said opening when they areremoved from said casing.
 13. An indicating instrument as claimed inclaim 11 further comprising a cover member adapted to cover saidopening.
 14. An indicating instrument as claimed in claim 1, saidreflector comprising:a first member for detachably holding said lightsource; and a second member detachably fixed to said casing.
 15. Anindicating instrument as claimed in claim 11, said reflector comprisinga second member for detachably holding said light source.
 16. Anindicating instrument for a vehicle, said instrument comprising:a dialplate; a longitudinally extending discharge lamp having a heater; alight conducting plate disposed on the back surface of said dial plate,said light conducting plate having a light incidence surface facing saiddischarge lamp; a reflector for reflecting light of said discharge lampto said light incidence surface, said discharge lamp being fixed to saidreflector; and a thermosensitive power supply circuit for supplyingelectric power to said heater according to a temperature of saiddischarge lamp.
 17. An indicating instrument as claimed in claim 16,wherein:said thermosensitive power supply circuit comprises athermosensitive element disposed near said discharge lamp, a battery anda switch connected between said battery and said heater, and said switchis controlled by said thermosensitive element.
 18. An indicatinginstrument as claimed in claim 16, wherein said switch is fixed to saidreflector.